U.S. patent application number 15/759743 was filed with the patent office on 2019-02-14 for a process for regenerating an adsorbent for nitrogen-containing compounds present in a hydrocarbon feed.
The applicant listed for this patent is ExxonMobil Chemical Patents Inc.. Invention is credited to Silvio Carrettin, Emiel De Smit, Joeri Denayer, Paul Hamilton, Mechilium J. G. Janssen, Anuschka Liekens, Luc R.M. Martens, Marianne F. M. Smits, Christopher J. Taylor, Mark R. Welford.
Application Number | 20190046957 15/759743 |
Document ID | / |
Family ID | 54199579 |
Filed Date | 2019-02-14 |
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United States Patent
Application |
20190046957 |
Kind Code |
A1 |
Carrettin; Silvio ; et
al. |
February 14, 2019 |
A Process For Regenerating An Adsorbent For Nitrogen-Containing
Compounds Present In A Hydrocarbon Feed
Abstract
A process for regenerating an adsorbent for nitrogen-containing
compounds present in a hydrocarbon feed comprising contacting the
adsorbent with an inert gas at a temperature in the range of from
10 to 60.degree. C., followed by contacting the adsorbent with an
inert gas at an elevated temperature in the range of from 200 to
260.degree. C. and cooling the adsorbent in an inert gas.
Inventors: |
Carrettin; Silvio;
(Kraainem, BE) ; Martens; Luc R.M.; (Vlaams
Brabant, BE) ; Hamilton; Paul; (Eastleigh, GB)
; Janssen; Mechilium J. G.; (Leuven, BE) ; De
Smit; Emiel; (Brussels, BE) ; Denayer; Joeri;
(Brussels, BE) ; Liekens; Anuschka; (Brussels,
BE) ; Smits; Marianne F. M.; (Mortsel, BE) ;
Welford; Mark R.; (Southampton, GB) ; Taylor;
Christopher J.; (Southampton, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ExxonMobil Chemical Patents Inc. |
Baytown |
TX |
US |
|
|
Family ID: |
54199579 |
Appl. No.: |
15/759743 |
Filed: |
July 13, 2016 |
PCT Filed: |
July 13, 2016 |
PCT NO: |
PCT/EP2016/066645 |
371 Date: |
March 13, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07C 7/04 20130101; C07C
7/005 20130101; B01J 20/3408 20130101; C10G 25/03 20130101; C07C
2529/70 20130101; C07C 7/13 20130101; C10G 57/02 20130101; C10G
2300/1088 20130101; C10G 2300/202 20130101; B01J 20/3483 20130101;
C07C 7/163 20130101; C10G 25/12 20130101; B01J 20/3466 20130101;
B01J 20/3458 20130101; C07C 2/12 20130101; C07C 7/13 20130101; C07C
11/10 20130101; C07C 7/005 20130101; C07C 11/10 20130101; C07C 7/04
20130101; C07C 11/10 20130101; C07C 7/163 20130101; C07C 11/10
20130101; C07C 2/12 20130101; C07C 11/02 20130101 |
International
Class: |
B01J 20/34 20060101
B01J020/34; C10G 57/02 20060101 C10G057/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 24, 2015 |
EP |
15186623.3 |
Claims
1. A process for regenerating an adsorbent for nitrogen-containing
compounds present in a hydrocarbon feed comprising the steps of a)
contacting the adsorbent with a stream comprising an inert gas at a
temperature in the range of from 10 to 60.degree. C.; b) followed
by contacting the adsorbent with a stream comprising an inert gas
at an elevated temperature in the range of from 200 to 260.degree.
C.; c) followed by cooling the adsorbent in an inert gas.
2. The process according to claim 1, wherein the inert gas is
selected from the group consisting of nitrogen, saturated
hydrocarbons and mixtures thereof.
3. The process of claim 1, wherein the stream used in steps (a),
and (b) comprises at least 96 wt %, preferably at least 98 wt %,
more preferably at least 99 wt % of at least one inert gas,
preferably nitrogen.
4. The process according to claim 1, wherein the stream used in
steps (a) and (b) comprises at least one inert gas, typically
nitrogen, and water, said process optionally further comprising
contacting the adsorbent from step (b) with an inert gas at a
temperature in the range of from 200 to 250.degree. C. in order to
remove water from the adsorbent before cooling according to step
(c).
5. The process according to claim 1, wherein the steam used in
steps (a) and (b) comprises at least 99.5 wt % nitrogen gas and the
nitrogen gas resulting from the regeneration may be washed with a
hydrocarbon having a low vapor pressure, in particular with a
hydrocarbon having 8 to 13 carbon atoms or mixture thereof.
6. The process according to claim 1, wherein the stream used in
steps (a) and (b) comprises at least 99 wt % of saturated
hydrocarbons having from 1 to 16 carbon atoms.
7. The process of claim 6, comprising an additional step (b')
between steps (a) and (b) at a temperature in the range of 80 to
110.degree. C.
8. The process according to claim 1, wherein the hydrocarbon feed
contaminated with at least one nitrogen containing compound is an
olefins containing feed also containing diolefins and/or cyclic
olefins and is preferably subjected to selective hydrogenation to
reduce the content of diolefins and/or cyclic olefins before
contact with the adsorbent.
9. The process according to claim 1, wherein the adsorbent
comprises a zeolite having faujasite structure, in particular
sodium zeolite Y (NaY) or sodium zeolite X (NaX) or a combination
thereof.
10. The process according to claim 1, wherein the elevated
temperature used in step (b) is in the range of from 220 to
240.degree. C.
11. The process according to claim 1, wherein water-containing
nitrogen gas is provided in the form of a stream characterized by
an inert gas flow of from 1 to 25 hr.sup.-1 WHSV and a water
partial pressure of from 1 to 20 kPa.
12. The process according to claim 1, wherein the regeneration
steps are conducted for a total period of from 12 to 144 hours,
each of steps (a) to (c) being preferably conducted for a period of
from 12 to 48 hours.
13. The process according to claim 1, wherein no further steps are
conducted that contribute to regeneration of the adsorbent.
14. The process according to claim 1, wherein the at least one
nitrogen containing compound is a nitrile, in particular
propionitrile (PCN).
15. A process for converting a hydrocarbon feed contaminated with
at least one nitrogen-containing compound into a hydrocarbon
product, said process comprising the steps of: i) providing a
hydrocarbon feed stream contaminated with at least one
nitrogen-containing compound; ii) contacting the feed stream with
an adsorbent to remove the nitrogen-containing compound(s) from the
feed; iii) contacting the feed stream having a reduced level of
nitrogen-containing compounds with a catalyst in order to convert
the feed stream into a hydrocarbon product; iv) regenerating the;
and, v) optionally, repeating steps (i) to (iii) or steps (i) to
(iv), wherein the regeneration step (iv) is as defined in claim
1.
16. The process according to claim 15, wherein the hydrocarbon feed
is an olefin containing feed further containing at least one of
diolefins or cyclic olefins.
17. The process according to claim 16, wherein the olefin is
selected from the group consisting of C.sub.3, C.sub.4, C.sub.5 and
C.sub.6 olefins and mixtures thereof, in particular C.sub.3,
C.sub.4 and C.sub.5 olefins, the hydrocarbon product comprises an
oligomerization product, and the oligomerization comprises a
material selected from the group consisting of zeolites, phosphoric
acids, supported metal oxides and combinations thereof.
Description
[0001] The present invention relates to a process for regenerating
an adsorbent for nitrogen-containing compounds present in a
hydrocarbon feed, such as a feed containing light olefins, i.e.,
typically C.sub.3 to C.sub.6 olefins, optionally containing at
least one of diolefins and cyclic olefins, wherein the adsorbent
used to remove the nitrogen-containing compound(s) from the feed is
regenerated in a multiple-step procedure such as a three-step
procedure comprising contacting the adsorbent with a stream
comprising an inert gas such as nitrogen or a saturated hydrocarbon
at different temperatures. The present invention also relates to a
process for converting a hydrocarbon feed contaminated with at
least one nitrogen containing compound into a hydrocarbon product,
said process comprising the use and regeneration of an adsorbent as
defined herein.
BACKGROUND
[0002] Hydrocarbon feeds containing light olefins, i.e., typically
C.sub.3 to C.sub.6 olefins are used in catalytic oligomerization
processes to obtain oligomers and/or polymers, typically octenes,
nonenes and dodecenes. These products may be converted to further
products such as alcohols, plasticizers, adipates, mercaptans and
solvents.
[0003] The hydrocarbon feed streams are derived from various
sources including refinery operations such as catalytic crackers
and steam crackers and are known to contain certain amounts of
impurities including but not limited to nitrogen containing
compounds such as nitriles. These impurities may have an adverse
effect on the catalysts used in the oligomerization process such as
phosphoric acid-based catalysts, zeolite-based catalysts and
supported metal catalysts, i.e., they may act as catalyst poisons
(contaminants) reducing the activity and service life of the
catalysts.
[0004] Prior art approaches to remove nitrogen-containing
contaminants include removal via liquid-liquid extraction
techniques or via adsorption techniques using a so-called guard
bed.
[0005] With regard to the use of guard beds, a number of approaches
have been developed in the prior art. For example, WO-A-2013/013885
describes a continuous process for converting a hydrocarbon feed,
such as a feed containing light olefins, contaminated with nitrile
compounds, into a hydrocarbon product, the process comprising the
steps of, in a first adsorber, contacting a hydrocarbon feed
comprising nitriles with at least one adsorbent in order to remove
nitriles from the feed; converting the feed with a reduced level of
nitriles into a hydrocarbon product; switching the flow of
hydrocarbon feed comprising nitriles from the first adsorber to a
second adsorber, and contacting the hydrocarbon feed comprising
nitriles with at least one adsorbent in said second adsorber in
order to remove nitriles from the feed; and, desorbing the nitriles
adsorbed on the at least one adsorbent of the first adsorber with a
portion of the hydrocarbon products. Thus, the process of
WO-A-2013/013885 uses a specific adsorber arrangement and
associated handling of feed and process streams to achieve a
reduced level of nitriles in the feed stream for a conversion
reaction such as olefin oligomerization. In the background of the
invention section of WO-A-2013/013885, it is mentioned that a spent
guard bed may be regenerated by heating under a flow of nitrogen or
under a flow of a hydrocarbon which is free of nitrile
contaminants.
[0006] US-A-2008/0194902 relates to the purification of
diene-contaminated liquid and gas streams by treating these streams
with adsorbents comprising single or multiple transition metal
polycation-exchanged faujasites having a certain silicon to
aluminum ratio, wherein the transition metal polycations have the
general formula [Tr.sub..alpha.O.sub..beta.].sup.n+, wherein
.alpha. varies from 2 to 8, .beta. varies from 0 to 4, and n varies
from 1 to 3, and wherein said transition metals is preferably
selected from the group consisting of copper, cadmium, zinc,
manganese, nickel and iron. In this context, a regeneration
procedure for the adsorbent is described in which the adsorbent is
first rinsed with hexene-1 at ambient temperature and at the same
flow rate as during adsorption followed by subjecting the adsorbent
bed to a hydrogen flow at a rate of 100 ml/min and at a gradually
raised temperature from ambient up to 180.degree. C.
[0007] Also, when using a guard bed to remove nitrogen-based
impurities such as nitriles, other impurities present in the feed
may detrimentally affect the efficient removal of the
nitrogen-based impurities. For example, diolefins and/or cyclic
olefins may have an affinity to the material used as the adsorbent
in a guard bed intended to remove nitrogen-based impurities. This
will result in competitive adsorption thereby reducing the
adsorption capacity and run time of a given adsorbent used in the
guard bed. Furthermore, coke formation due to the reaction of
diolefins (linear and cyclic) present in a stream during adsorption
and desorption may be a problem.
[0008] Thus, there remains a need for further processes which allow
for an efficient removal of nitrogen-based impurities while
allowing at the same time for increased run time of the process and
process materials such as the adsorbents for the nitrogen
contaminants.
SUMMARY OF THE INVENTION
[0009] According to a first aspect, the present invention solves
the above problem(s) by a process for regenerating an adsorbent for
nitrogen-containing compounds present in a hydrocarbon feed, said
process comprising the steps of [0010] a) contacting the adsorbent
with a stream comprising an inert gas at a temperature in the range
of from 10 to 60.degree. C., [0011] b) followed by contacting the
adsorbent with a stream comprising an inert gas at an elevated
temperature in the range of from 200 to 260.degree. C.; [0012] c)
followed by cooling the adsorbent in an inert gas.
[0013] Preferably, the inert gas is selected from the group
consisting of nitrogen, saturated hydrocarbons and mixtures
thereof.
[0014] According to one embodiment the stream used in steps (a),
and (b) comprises at least 96 wt %, preferably at least 98 wt %,
more preferably at least 99 wt % of at least one inert gas.
[0015] According to another embodiment, the stream used in steps
(a) and (b) comprises at least one inert gas, typically nitrogen,
and water and is preferably a water-saturated inert gas.
[0016] Such process may further comprises contacting the adsorbent
from step (b) in a dry inert gas, preferably dry nitrogen, at a
temperature in the range of from 200 to 250.degree. C. in order to
remove water from the adsorbent before cooling according to step
(c). The water is usually present in the stream at a partial
pressure of from 0.1 to 20 kPa, preferably from 1 to 20 kPa. Water
partial pressure less than 1.5 kPa, preferably between 0.7 and 1.2
kPa provides good results.
[0017] According to another embodiment, the stream used in steps
(a) and (b) comprises at least 99 wt %, preferably at least 99.5 wt
% nitrogen gas and the nitrogen gas resulting from the regeneration
may be washed with a hydrocarbon having a low vapor pressure, in
particular with a hydrocarbon having 8 to 13 carbon atoms.
[0018] According to another embodiment, the stream comprises at
least 98, preferably at least 99, and more preferably at least 99.5
wt % of one or more saturated hydrocarbons having from 1 to 16
carbon atoms. Mixtures of saturated hydrocarbon comprising from 7
to 12 carbon atoms as well as mixtures of saturated hydrocarbons
comprising from 5 to 6 carbon atoms provide good results. Saturated
hydrocarbon mixtures having a boiling range within the temperature
range of 120 to 220.degree. C., or 50 to 80.degree. C. may also be
preferred.
[0019] It goes without saying that, depending on the process
conditions used in said steps (a) and (b), the stream contains
liquid in equilibrium with its gas phase.
[0020] According to a second aspect, the present invention relates
to process for converting a hydrocarbon feed contaminated with at
least one nitrogen-containing compound into a hydrocarbon product,
said process comprising the steps of: [0021] i) providing a
hydrocarbon feed stream contaminated with at least one
nitrogen-containing compound; [0022] ii) contacting the feed stream
with an adsorbent to remove the nitrogen-containing compound(s)
from the feed; [0023] iii) contacting the feed stream having a
reduced level of nitrogen-containing compounds with a catalyst in
order to convert the feed stream into a hydrocarbon product; [0024]
iv) regenerating the adsorbent; and, [0025] v) optionally,
repeating steps (i) to (iii) or steps (i) to (iv), wherein the
regeneration step (iv) is as defined in accordance with the first
aspect of the present invention.
[0026] The hydrocarbon feed stream used in this invention may be
contaminated with other compounds having an affinity to adsorbents
such as oxygenates, sulphur-containing compounds, water, diolefins
and mixtures thereof. Such hydrocarbon feed may be subjected to
further treatment(s) such as distillation and/or reduction before
contacting with the adsorbent to reduce the content of said other
compounds.
[0027] According to other embodiments, the hydrocarbon feed stream
contaminated with at least one nitrogen containing compound is an
olefins containing feed that optionally contains at least one of
diolefins. Such hydrocarbon feed stream is preferably further
subjected to selective hydrogenation to reduce the content of
diolefins before contact with the adsorbent.
[0028] In a preferred embodiment, at least one nitrogen containing
compound is a nitrile, in particular propionitrile (PCN) or
acetonitrile (ACN).
[0029] Further and preferred embodiments are disclosed in the
dependent claims and in the following description including the
examples and figures illustrating the present invention.
BRIEF DESCRIPTION OF THE FIGURES
[0030] FIG. 1 is a graphic representation of adsorbent service life
in terms of the level of nitrogen-containing contaminants present
in the feed passing over the adsorbent before and after
regeneration cycles using decene.
[0031] FIG. 2 is another graphic representation of adsorbent
service life in terms of the level of nitrogen-containing
contaminants present in the feed passing over the adsorbent before
and after regeneration cycles using decene.
[0032] FIG. 3 is another graphic representation of adsorbent
service life in terms of the level of nitrogen-containing
contaminants present in the feed passing over the adsorbent before
and after regeneration with decene and a water-saturated nitrogen
stream.
[0033] FIG. 4 is another graphic representation of adsorbent
service life in terms of the level of nitrogen-containing
contaminants present in the feed after passing over the adsorbent
before and after regeneration with a water-saturated nitrogen
stream.
[0034] FIG. 5 is another graphic representation of adsorbent
service life in terms of the level of nitrogen-containing
contaminants present in the feed passing over the adsorbent before
and after regeneration with dry nitrogen.
[0035] FIG. 6 is another graphic representation of adsorbent
service life in terms of the level of nitrogen-containing
contaminants present in the feed passing over the adsorbent before
and after regeneration with water-saturated nitrogen and using a
feed subjected to hydrogenation prior to passing over the
adsorbent.
[0036] FIG. 7 is another graphic representation of adsorbent
service life in terms of the level of nitrogen-containing
contaminants present in the feed after passing over the adsorbent
before and after regeneration with water-saturated nitrogen and
using a feed subjected to distillation prior to passing over the
adsorbent.
[0037] FIG. 8 is a process scheme showing the disposition of
nitrogen-rich regeneration gas by contacting the gas with
hydrocarbons having a low vapor pressure.
[0038] FIG. 9 is a graphic representation of the adsorbent capacity
after multiple regeneration runs using different regeneration
schemes.
DETAILED DESCRIPTION OF THE INVENTION
[0039] Before the materials, compounds, components, compositions
and/or processes of the present invention are disclosed in more
detail, it is noted that the singular forms "a", "an" and "the"
include plural referents unless otherwise specified.
[0040] Furthermore, the words "comprising" (and any form of
comprising such as "comprise" and "comprises"), "having" (and any
form of having, such as "have" and "has"), "including" (and any
form of including, such as "includes" and ("include") or
"containing" (and any form of containing, such as "contains" and
"contain") are inclusive or open-ended and do not exclude
additional, unrecited elements such as materials, compounds or
compositions or additional process steps.
[0041] The terms "feed" and "feedstock" are used herein
interchangeably to refer to the hydrocarbon feed used in this
invention. Typically the hydrocarbon feed contains at least one
light olefins such as a C.sub.3 to C.sub.6 olefin. When applicable,
said feed may also be referred to as "olefin feed".
[0042] The hydrocarbon feed is characterized by comprising a
certain level of nitrogen containing compounds and, optionally,
certain levels of other compounds such as oxygenates
sulphur-containing compounds, water, diolefins, cyclic olefins and
mixtures thereof, preferably diolefins and/or cyclic olefins having
an affinity to adsorbents for nitrogen compounds, said adsorbents
being disclosed in detail in the following description and appended
claims. The levels (concentrations) of both the nitrogen and said
other compounds are usually in a range referred to as impurities or
at least as minor components of the stream. In particular, with
regard to nitrogen and other heteroatom containing compounds, the
concentrations of this type of compounds will usually be in the
range of from 0.1 to several hundred weight ppm (wt ppm), typically
in a range of from 10 to 500 wt ppm, relative to the total weight
of the stream. With regard to non-heteroatom containing compounds,
such as dienes, the concentrations of this type of compounds will
typically be in the range of from 0.01 to 5 or 10 weight % (wt %)
relative to the total weight of the stream. In this context, the
phrase "other compounds having an affinity to adsorbents for
nitrogen containing compounds" means that the respective compound
interacts with an adsorbent suitable to adsorb nitrogen containing
compounds such as nitriles in a manner that reduces the adsorbent's
capacity for adsorbing said nitrogen containing compounds, e.g.,
due to competitive adsorption. The adsorption step used in this
invention is capable of reducing the content of nitrogen containing
compounds in the hydrocarbon feed from an initial range of from 10
to 500 wt ppm to the range of from 20 to 500 wt ppb relative to the
weight of the feed.
[0043] According to one embodiment, the hydrocarbon feed containing
other compounds having an affinity to the adsorbent is subjected to
at least one distillation step prior to contacting with the
adsorbent to provide one or more fractions having a reduced level
of said other compounds and said fraction(s), optionally combined
together, are contacted with the adsorbent to remove the nitrogen
containing compounds.
[0044] In another embodiment of the present invention, the
hydrocarbon feed contaminated with at least one nitrogen containing
compound contains diolefins and/or cyclic olefins and is preferably
subjected to selective hydrogenation to reduce the content of
diolefins and optionally cyclic olefins before contact with the
adsorbent. This embodiment is particularly used if the levels of
dienes in the feed are within the range of 0.01 to 10 weight % (wt
%) relative to the total weight of the stream mentioned above.
[0045] In further embodiments of the present invention, compounds,
components, compositions and processes as disclosed herein can
consist of the features disclosed in these respects.
Regeneration
[0046] As stated above, according to a first aspect, the present
invention solves the above problem(s) by a process for regenerating
an adsorbent for nitrogen-containing compounds present in a
hydrocarbon feed, said feed preferably being a olefins containing
feed that optionally also contains at least one of diolefins and
cyclic olefins, said process comprising the steps of [0047] a)
contacting the adsorbent with a stream comprising an inert gas at a
temperature in the range of from 10 to 60.degree. C., preferably 20
to 50.degree. C., such as 40.degree. C.; [0048] b) followed by
contacting the adsorbent with a stream comprising an inert gas at
an elevated temperature in the range of from 200 to 260.degree. C.;
preferably 220 to 240.degree. C., such as 230.degree. C.; [0049] c)
followed by cooling the adsorbent in an inert gas, preferably to a
temperature at or above ambient temperature such as 40.degree.
C.
[0050] Preferably, the inert gas is selected from the group
consisting of nitrogen, saturated hydrocarbons and mixtures
thereof. The inert gases used in each of steps (a) to (c) may be
the same or may be different. Preferably the same inert gas is used
in each of these steps.
[0051] According to one embodiment the stream used in step (a), and
(b) consists essentially in an inert gas comprises at least 99 wt
%, preferably at least 99.5 wt %, typically 99.9 wt % of at least
one inert gas, typically nitrogen. The impurities in such inert gas
usually, include oxygen, hydrogen, carbon monoxide and carbon
dioxide. Such impurities are usually present in an amount less than
1000 ppm by weight, preferably less than 100 and more preferably
less than 10 ppm by weight.
[0052] Additionally, when the gas steam used in steps (a) and (b)
comprises at least 99 wt % nitrogen gas, the nitrogen gas resulting
from the regeneration may be washed with a hydrocarbon having a low
vapor pressure, in particular with a hydrocarbon having from 5 to
13 carbon atoms or mixtures such hydrocarbons. Octene, isooctane,
octane or dodecane or mixtures thereof are advantageously used. The
preferred nitrogen to hydrocarbon ratio (wt/wt) is between about
0.5 and 2.
[0053] According to another embodiment, the stream used in steps
(a) and (b) comprises at least one inert gas and water and is
preferably a water-saturated nitrogen. Such process may further
comprises contacting the adsorbent from step (b) in a dry inert
gas, preferably dry nitrogen, at a temperature in the range of from
200 to 250.degree. C. in order to remove water from the adsorbent
before cooling according to step (c). The duration of this step is
usually in the range of from 1 to 36 hours. Such a process while
providing satisfactory regeneration performances may be disregarded
for economic reasons.
[0054] According to another embodiment, the stream comprises at
least 98, preferably at least 99, and more preferably at least 99.5
wt % of one or more saturated hydrocarbons having from 1 to 15
carbon atoms. Mixtures of saturated hydrocarbon comprising from 7
to 12 carbon atoms as well as mixture of saturated hydrocarbons
comprising from 5 to 6 carbon atoms provide good results. Saturated
hydrocarbon mixtures having a boiling range within the temperature
range of 120 to 220.degree. C., or 50 to 80.degree. C. are also
preferred.
[0055] The elevated temperature used in step (b) is preferably in
the range of from 220 to 240.degree. C.
[0056] The flow of the stream in steps (a) and (b) is usually in
the Weight Hourly Space Velocity (WHSV) range of from 0.1 to 60
hrs.sup.-1, preferably from 0.5 to 40 hrs.sup.-1 most preferably
from 1 to 30 hrs.sup.-1.
[0057] In order to obtain a stream of inert gas comprising water,
preferably a water-saturated stream of inert gas, the regeneration
stream can be hydrated using a water saturator. The temperature of
the water saturator will determine the water partial pressure in
the regeneration stream. A preferred saturator temperature is
between 25 and 90.degree. C.
[0058] Alternatively, water can be co-fed with the inert gas
regeneration stream in the right proportion to saturate the
regeneration stream with water in a suitable temperature range,
preferably in the range of from 25 to 90.degree. C.
[0059] The above approaches are known to a person skilled in the
art. For example, with regard to water partial pressure/water
solubility as a function of temperature for hydrocarbons, see,
e.g., P. Schatzberg, Solubilities of Water in Several Normal
Alkanes from C7 to C16, Journal of Physical Chemistry, Vol. 67,
776-770 (1963) or A. Bahadori et al., Predicting Water-Hydrocarbon
Systems Mutual Solubility, Chem. Eng. Technol. 2008, 31, No. 12,
1743-1747. For inert gases such as nitrogen see, e.g., the Handbook
of Chemistry and Physics, 58th Edition, pp.D-180-D-181.
[0060] Water-containing nitrogen gas is preferably provided in the
form of a stream characterized by an inert gas flow of from 1 to 25
h.sup.-1 WHSV.
[0061] The regeneration steps (a) to (c) of the process according
to the first aspect may be conducted for a period sufficient to
restore at least 75% of the adsorbent's original adsorption
capacity, as determined by the amount of contaminated feed passed
over the adsorbent before the adsorbent becomes ineffective, as
indicated by an increase (breakthrough) in the level of
nitrogen-containing compounds in the feed after contact with the
adsorbent.
[0062] For example, the regeneration steps are conducted for a
total period of from 12 to 144 hours. Each of steps (a) to (c) may
be conducted for a period of from 3 to 48 h, typically of from 3 to
15 hours. Periods of from 12 to 48 hours are also suitable.
[0063] The increase of temperature between step (a) and step (b)
can be done continuously or stepwise.
[0064] For example, and more particularly when the stream used in
steps (a) and (b) consists essentially in a saturated hydrocarbon
stream, the increase of temperature preferably comprises an
additional step (b') between steps (a) and (b) at a temperature in
the range of 80 to 110.degree. C. In such a case regeneration step
(a) may be conducted for a period of 3 to 7 hours, and steps (b')
and (b) for a period of from 4 to 8 hours.
[0065] The pressure employed during regeneration may be in the
range of from about 14.5 psia to about 290 psia (100 kPa to 2000
kPa), and preferably from about 14.5 psia to about 145 psia (100
kPa to 1000 kPa).
[0066] According to the present invention, no further process steps
are preferably conducted that contribute to regeneration of the
adsorbent other than those described in the context of the first
aspect of the present invention.
Adsorbents
[0067] Examples of suitable adsorbents include alumina (aluminium
oxide), preferably gamma alumina or eta alumina, molecular sieves,
zeolites (acidic or cation-exchanged), activated carbons, clays,
optionally impregnated with metals, metal oxides and mixed metal
oxides, silica gels, resins (e.g., acid resins) and combinations
thereof.
[0068] Examples of metal oxides other than alumina include tin
oxide, zirconium oxide, titanium oxide, iron oxide, magnesium and
tungsten oxide, silicon oxide, copper oxide, nickel oxide, zinc
oxide, and mixtures thereof. The adsorbent can comprise two or more
of the metal oxides listed above and in any combination.
[0069] Exemplary materials and methods for making and using
adsorbers are described, for example, in EP-A-1 002 852 and
US-A-2005/0137442. Furthermore, processes and adsorbers as
disclosed in WO 2013/013884; WO 2013/013885; WO 2013/013886; WO
2013/013887; and WO 2013/013888 may be used. In this context, it is
noted that the term "adsorber" is used to refer to a unit
containing an adsorbent.
[0070] Other specific examples include without limitation molecular
sieve 3A (activated 16 h @ 200.degree. C. & vacuum), molecular
sieve 13X (activated 1 h @ 200.degree. C. & vacuum),
ZEOLYST.TM. CBV 100 CY (Zeolite Na-Y, white rods (80/20
FAU/Binder)), Cameron SG6 carbon (12*40 mesh, coconut shell based
BCT 4443), Cameron SG6 carbon (8*30 mesh, coconut shell based, BCT
4444), Norit GAC 830W 640316, BCT 4475 active coal, Kieselgel Fein
silicagel (MN), Amberlyst 15 A, silica bound ex fr F103runE60, and
Alcoa Selexsorb.TM..
[0071] Preferably the adsorbent comprises a zeolite with faujasite
(FAU) structure optionally formulated together with a suitable
binder material. The weight ratio of zeolite to binder may be in
the range of from 50:50 to 90:10, such as 70:30 to 80:20. The
formulated zeolite/binder adsorbent may be provided in the form of
particles of desired shape, such as rod-like or sphere-like
particles.
[0072] Examples of binder materials that may be employed with the
molecular sieves or zeolites suitable for use in the process of the
invention include active and inactive materials and synthetic or
naturally occurring zeolites as well as inorganic materials such as
clays, silica and/or metal oxides such as alumina. Examples of
other materials include porous matrix materials such as
silica-alumina, silica-magnesia, silica-zirconia, silica-thoria,
silica-beryllia, silica-titania as well as ternary compositions
such as silica-alumina-thoria, silica-alumina-zirconia,
silica-alumina-magnesia and silica-magnesia-zirconia.
[0073] The preferred zeolites with faujasite structure comprise
Zeolite X or Zeolite Y. The most preferred adsorbents include
sodium Zeolite Y (NaY) and sodium Zeolite X (NaX).
[0074] The preferred zeolite adsorbents of the present invention
are characterized by the fact that at least 95% of the available
cation sites are occupied by sodium cations. More preferably, 99%
of the available cation sites are occupied by sodium cations and
even more preferably 99.9% of the available cation sites are
occupied by sodium cations. Such zeolite structure is considered by
the person of ordinary skill in the art as non acidic zeolite
structure.
[0075] The adsorption may be carried out at lower temperatures,
such as down to -5.degree. C., at room temperature (i.e., at about
15 to 20 or 25.degree. C.) or at elevated temperatures, and thus
conveniently takes place in the range of -5 to 250.degree. C.
Preferably, adsorption is carried out in the temperature range of
20 to 80.degree. C., such as 40.degree. C. to 60.degree. C.
[0076] The pressure employed during adsorption may be in the range
of from about 400 psig to about 4000 psig (2860 kPa to 27688 kPa),
and preferably from about 500 psig to about 1500 psig (3550 kPa to
10446 kPa). The hydrocarbon feed weight hourly space velocity may
be in the range of from about 0.1 hr.sup.-1 to about 20 hr.sup.-1,
and preferably from about 0.5 hr.sup.-1 to about 5 hr.sup.-1.
Hydrocarbon Feed
[0077] The hydrocarbon feed provided in the processes according to
the aspects of the present invention can be any hydrocarbon feed
contaminated with nitrogen containing compounds, including aromatic
or aliphatic hydrocarbons or a combination thereof. Whilst the
process of the present invention is not limited by hydrocarbon feed
or the type of process for which the hydrocarbon feed is used,
preferably the process of the present invention is part of an
olefin oligomerization process and the hydrocarbon feed is an
olefin containing feed. In particular, the feed is a C.sub.3,
C.sub.4 and/or C.sub.5 olefin containing stream, more preferably a
C.sub.5 olefin containing stream.
[0078] As used herein, "olefins" refers to any unsaturated
hydrocarbons having the formula C.sub.nH.sub.2n, wherein C is a
carbon atom, H is a hydrogen atom, and n is the number of carbon
atoms in the olefin. According to this invention, the olefins in
the feed typically have from 2 to 15 carbon atoms, such as at least
3 and no more than 8 carbon atoms, and typically at least 3 and no
more than 6 carbon atoms. They are also referred to as lower or
light olefins. According to a preferred embodiment, the feed is a
C.sub.3, C.sub.4 and/or C.sub.5 olefin containing stream, more
preferably a C.sub.5 olefin containing stream.
[0079] The feed may also comprise one or more paraffins. As used
herein, "paraffins" refers to any of the saturated hydrocarbons
having the formula C.sub.nH.sub.2n+2 wherein C, H and n are defined
here above. The paraffins that may be present in the olefin feed
typically have from 1 to 25 carbon atoms, such as from 1 to 15
carbon atoms, and conveniently at least 3 and no more than 6 carbon
atoms. Examples of suitable paraffins include methane, ethane,
propane, butane, pentane, hexane, isomers thereof and mixtures
thereof. If present in the feed, the paraffins may have the same or
a different number of carbon atoms as the olefins.
[0080] If present, the paraffin usually acts as a diluent. If used,
the olefin feed may comprise at least 10%, at least 25%, at least
30%, at least 35%, or at least 40% paraffin, based upon the total
volume of the feed. Alternatively stated, if used, the diluent may
be present in the olefin feed in the range from 10% to 40%,
alternatively, from 10% to 35%, and alternatively, from 20% to 35%
based upon the total volume of the feed. The diluent may also be
fed to the reactor(s) separately from the olefin feed. When fed
separately, the diluent may be fed in amounts equivalent to those
mentioned above, where the diluent is co-fed with the feed.
[0081] In a class of embodiments, the olefin containing feed
comprises olefins selected from propene, butenes, pentenes,
hexenes, their isomers, and mixtures thereof. The process of this
invention is especially useful for the oligomerization of feeds
comprising propene, butenes, pentenes, their isomers, and mixtures
thereof. As used herein, "isomers" refers to compounds having the
same molecular formula but different structural formula.
[0082] Additionally, the feed may comprise an oligomer (higher
olefin), for example, a dimer, such as one provided by recycling a
part of an olefin oligomerization product stream. As used herein,
"oligomer(s)" or "oligomer product" refers to an olefin (or a
mixture of olefins) made from a few light olefins. For example,
oligomers include dimers, trimers, tetramers, obtained from two,
three or four light olefins of the same number of carbon atoms,
mixed oligomers, obtained from 2 or more olefins having different
numbers of carbon atoms and mixtures thereof. In a class of
embodiments, "oligomer(s)" refers to an olefin (or a mixture of
olefins) having 20 carbon atoms or less, alternatively, 15 carbon
atoms or less, such as 10 carbon atoms or less, alternatively, 9
carbon atoms or less, and conveniently, 8 carbon atoms or less.
[0083] In a class of embodiments, the feed comprises 30 wt % or
more olefins, such as 40 wt % or more olefins, alternatively, 50 wt
% or more olefins, alternatively, 60 wt % or more olefins,
alternatively, 70 wt % or more olefins, and alternatively, 80 wt %
or more olefins, based upon the total weight of the feed.
[0084] In any of the olefin oligomerization embodiments described
herein, the feed should be totally free, or at least substantially
free, of aromatic hydrocarbon compounds that consist solely of
hydrogen and carbon atoms. In this context, "substantially free"
means that the olefin feed contains 25 wt % or less, preferably 15
wt % or less, more preferably 10 wt % or less, such as 5 wt % or
less, and most preferably 1 wt % or less aromatic hydrocarbon,
based upon the total weight of the olefin feed.
[0085] Examples of suitable olefin feeds include untreated refinery
streams such as Fluidized Catalytic Cracking (FCC) streams, steam
cracker streams, coker streams, pyrolysis gasoline streams or
reformates.
[0086] Examples of suitable C.sub.3 olefin containing feedstreams
include untreated C.sub.3 rich refinery streams such as "dilute" or
"refinery grade" propylene from a Fluidized Catalytic Cracker
(FCC), C.sub.3 rich stream from a steam cracker, from the
production of "chemical grade" or "polymer grade" propylene, from
refinery gas recovery units, from Propane Dehydrogenation Units,
from Gas to Olefin (GTO) Units, or from Fisher-Tropsch Units, and
C.sub.3 rich return streams from polypropylene producing units.
These C.sub.3 streams may contain for example from 50 to 60 wt % of
propylene, or 65 wt % or more, or 70 wt % or above such as 72 wt %
or 75 wt % or even up to 79 wt %. The C.sub.3 streams containing
from 5 to 95 wt % of propylene are suitable
[0087] Examples of suitable C.sub.4 olefin containing feeds include
refinery feeds often referred to as Raffinate-1 (RAF-1),
Raffinate-2 (RAF-2) or Raffinate-3 (RAF-3). Typically, Raffinate-1,
Raffinate-2 and Raffinate-3 may be regarded as streams obtainable
at various stages in the processing of crude C.sub.4 streams
obtained from petroleum refining processes. These streams are well
known by the person skilled in the art.
[0088] In another embodiment, the feed comprises an FCC light
olefin stream that typically comprises ethane, ethylene, propane,
propylene, isobutane, n-butane, butenes, pentenes, pentanes, and
other optional components, preferably in the amounts as disclosed
hereinabove.
[0089] Examples of suitable C5 olefin feeds include FCC Light
Naphtha streams, steam cracker C5 rich streams that have been
treated for diene removal, C5 olefin containing streams from Gas to
Olefin (GTO) Units, or Fisher-Tropsch Units. In this context,
"Light Naphtha" is understood to mean a stream having a specific
gravity in the range 0.65 to 0.73. An ASTM-D86 boiling point range
between 35 and 125.degree. C. and that contains a range of olefin,
paraffin, diolefins and cyclic hydrocarbon compounds with carbons
numbers typically in the range C5 to C8. More specifically,
according to an embodiment, a so-called Light Light Catalytic
Naphtha stream may be used. Such stream is characterized by a
boiling point range of, for example, from 25 to 70.degree. C. at
atmospheric pressure and a specific gravity between 0.63 and 0.68
and contains at least 60 wt % C5 hydrocarbons.
[0090] These streams may comprise C.sub.5 olefin components in the
amounts as disclosed hereinabove. For example, an FCC Light Naphtha
stream may comprise 50 wt % or more C.sub.5 olefins, alternatively,
60 wt % or more C.sub.5 olefins, alternatively, 70 wt % or more
C.sub.5 olefins, and preferably, 80 wt % or more C.sub.5 olefins,
based upon the total weight of the olefin feed. Additional
distillations may be required to achieve the desired C.sub.5 olefin
content. These ranges also apply to the other specific C.sub.5
olefin containing streams disclosed above.
[0091] According to the present invention, any of the
above-described feeds contains nitrogen containing compounds and
other impurities acting as catalyst contaminants which must be
removed to an acceptable level before the hydrocarbon feed
undergoes a catalyzed reaction. In particular, the nitrogen
containing compounds comprise nitriles. As used herein, "nitrile"
is any organic compound that has a nitrile group (or --C.ident.N
functional group). In the nitrile group, the carbon atom and the
nitrogen atom are triple bonded together. As used herein,
"acetonitrile" (ACN) is the chemical compound with formula
CH.sub.3CN. This colorless liquid is the simplest organic nitrile.
As used herein, "propanenitrile", "propionitrile", or "ethyl
cyanide" is a nitrile with the molecular formula C.sub.2H.sub.5CN
and the terms may be used interchangeably. It is also a clear
liquid. Preferably the nitrile removed is a C.sub.2 to C.sub.5
nitrile. In the most preferred embodiment the nitrile to be removed
is any of acetonitrile and propionitrile. These compounds are
especially toxic to oligomerization catalysts and their removal
leads to significant catalyst life improvement.
[0092] According to the present invention, any of the
above-described feeds optionally contains at least one of diolefins
and/or cyclic olefins. These compounds may also act as catalyst
contaminants and are removed by the adsorption process used in this
invention. In particular the dienes are hydrocarbons containing two
carbon double bonds. The dienes concerned by this invention include
but are not limited to C.sub.4 to C.sub.10 dienes. The cyclic
olefins concerned by this invention include but are not limited to
C.sub.4 to C.sub.10 hydrocarbon ring having at least one carbon
carbon double bond. The double bond is preferably part of the
cycle. Typical cyclic compounds are cyclopentene,
methylcyclohexene, cyclohexene and cycloheptene.
Distillation and Hydrogenation
[0093] Prior to contacting the hydrocarbon feed with the adsorbent,
the feed may be subjected to distillation and/or hydrogenation in
order to change and/or improve desired properties of the feed.
[0094] The distillation/hydrogenation process may be used to reduce
the level of compounds having an affinity to adsorbents for
nitrogen-containing compounds other than the nitrogen containing
compounds themselves. In particular, such compounds may be
oxygenates, sulphur containing compounds, water, dienes and
mixtures thereof. In this context, as used herein, the term
"oxygenates" includes oxygen containing organic compounds including
but not necessarily limited to aliphatic alcohols, ethers, carbonyl
compounds (aldehydes, ketones, carboxylic acids, carbonates, and
the like). It is to be noted that water is not considered herein as
an oxygenate. Thus, when reference is made therein to the level of
oxygenates present in a feed, this level does not include water.
The sulphur compounds may include, but are not limited to
methanethiol, ethanethiol, di-methyl-sulfide, carbon-di-sulfide,
propanethiol and thiophene. The dienes concerned by this invention
include but are not limited to C.sub.4 to C.sub.10 dienes.
[0095] Prior to the at least one distillation step, the feed may
comprise the following first levels of nitrogen containing and
other compounds having an affinity to adsorbents for nitrogen
containing compounds.
[0096] The first level of nitrogen containing compounds may be in
the range of from 0.1 wt ppm to 100 wt ppm, such as 3 wt ppm or
more, such as about 5 wt ppm or more, typically, 10 wt ppm or more,
such as 20 wt ppm or more, and yet alternatively, 30 wt ppm or more
up to 100 wt ppm, based on the amount of nitrogen present in the
compounds relative to the total weight of the stream.
[0097] The first level of oxygenates may be in the range of from
0.1 wt ppm to 500 wt ppm, relative to the total weight of the
stream.
[0098] The first level of sulphur containing compounds may be in
the range of from 0.1 to 100 wt ppm, expressed as the amount of
sulphur present in the compounds relative to the total weight of
the stream.
[0099] The first level of water may be in the range of from 0.1 wt
ppm to 300 wt ppm relative to the total weight of the stream.
[0100] The first level of dienes or cyclic olefins may be in the
range of from 0.01 wt % to 5 wt % relative to the total weight of
the stream.
[0101] The distillation is usually carried out through use of
trayed columns, packed columns including structured packing, random
packing or a combination of both, combinations of trays and
packing, e.g., in divided wall columns.
[0102] The distilled fractions and or combination thereof are then
passed over the adsorbent to reduce the level of nitrogen
containing compounds present in the feed.
[0103] The specific selection and blending of fractions will
usually depend on the details of the composition of the feed
stream. Also, the details of subsequent processing for converting
the hydrocarbon feed into a desired hydrocarbon product may
influence the selection and blending of fractions obtained from
distillation step. For example, oligomerization, alkylation,
isomerization conversion processes may use different catalysts at
different process conditions and with different catalyst
performance targets which will have an impact on acceptable levels
of impurities which in turn can be controlled by selecting and
blending distillation fractions as described above.
[0104] The distillation is preferably carried out to eliminate the
bottom and top fractions of the hydrocarbon feed so that the
combined stream the fraction(s) obtained in the distillation
represent the "heart cut" of the hydrocarbon feed. Particularly
advantageous results may be obtained when the high boiling fraction
are completely eliminated before the absorption step. The combined
or blended fractions preferably have a boiling range of from
27.degree. C. to 37.degree. C. Typically the initial boiling point
is 27.5, more preferably of 28.2.degree. C. The T95 of the combined
or blended fraction is of at most 35.degree. C. typically at most
33.degree. C.
Hydrocarbon Conversion
[0105] According to the second aspect, the present invention
relates to process for converting a hydrocarbon feed contaminated
with at least one nitrogen-containing compound into a hydrocarbon
product, said process comprising the steps of: [0106] i) providing
a hydrocarbon feed stream contaminated with at least one
nitrogen-containing compound; [0107] ii) contacting the feed stream
with an adsorbent to remove the nitrogen-containing compound(s)
from the feed; [0108] iii) contacting the feed stream having a
reduced level of nitrogen-containing compounds with a catalyst in
order to convert the feed stream into a hydrocarbon product; [0109]
iv) regenerating the adsorbent comprising contacting the adsorbent
with a gas atmosphere; and, [0110] v) optionally, repeating steps
(i) to (iii) or steps (i) to (iv), wherein the regeneration step is
as defined above.
[0111] The process for converting the hydrocarbon feed into a
hydrocarbon product concerned by this invention may be an
isomerization, an alkylation, a hydrogenation, an aromatization or
an oligomerization process, preferably such process is an
isomerization or an oligomerization process.
[0112] Typically the process of the present invention is an olefin
oligomerization process and the hydrocarbon feed is an olefin
containing feed as described above. As used herein,
"oligomerization process" refers to any process by which light
olefins are linked together to form the oligomer(s) as defined
herein. As used herein, the term "oligomerization conditions"
refers to any and all those variations of equipment, conditions
(e.g. temperatures, pressures, weight hourly space velocities
etc.), materials, and reactor schemes that are suitable to conduct
the oligomerization process to produce the oligomer(s) as known and
applied in the art and discussed in more detail below.
[0113] In a preferred embodiment, the hydrocarbon feed comprises an
olefin, wherein the olefin is preferably selected from the group
consisting of C.sub.3, C.sub.4, C.sub.5 and C.sub.6 olefins and
mixtures thereof, in particular C.sub.3, C.sub.4 and C.sub.5
olefins.
[0114] In a preferred embodiment, the hydrocarbon product comprises
an oligomerization product and the catalyst is an oligomerization
catalyst comprising a material selected from the group consisting
of zeolites, phosphoric acids, supported metal oxides and
combinations thereof. Preferably, the oligomerization catalyst
comprises a zeolite, in particular a zeolite selected from the
group consisting of ZSM-22, ZSM-57, ZSM-5, ITQ-39 and combinations
thereof.
[0115] In a preferred embodiment, the oligomerization product is
further subjected to any of the following steps: fractionation,
hydrogenation, hydroformylation, oxidation, carbonylation,
etherification, epoxidation, hydration or a combination
thereof.
[0116] As noted above, one or more catalysts may be used in
oligomerization processes of several embodiments of the invention.
Any catalyst may be used so long as it is suitable to oligomerize
olefins. Both homogeneous and heterogeneous catalysts may be
used.
[0117] An example of a homogeneous catalyst includes the IFP (now
Axens) DIMERSOL processes which employ a Ni-based homogeneous
catalyst. (See, for example, Y. Chauvin et al., Chemistry and
Industry, 1974, pages 373-378 and U.S. Pat. No. 3,655,810.)
Additionally, U.S. Pat. No. 4,225,743 discloses a homogeneous
catalyst system consisting of a nickel (II) salt of octanoic acid,
ethylaluminium dichloride, and a free fatty acid.
[0118] In contrast, several of the industrial processes use
heterogeneous catalysts. Most of these catalysts belong to one of
the following groups: a) mineral acids (e.g., sulfuric acid or
phosphoric acid) on a support material (e.g., alumina or silica),
b) zeolites or other aluminum silicates, "undoped" or "doped" by
further metals, in particular, for example, with transition metals,
and c) acidic ion exchange resins. Examples are described in
US-A-2004/0097773.
[0119] Heterogeneous catalysts may be divided into crystalline and
amorphous (non-crystalline) catalyst categories. Crystalline
catalysts include, without limitation, molecular sieve catalysts
such as, for example, zeolite catalysts. Non-crystalline catalysts
include, without limitation, solid acid catalysts such as, for
example, solid phosphoric acid catalyst (sPa) and supported metal
catalysts or supported metal oxide catalysts. Examples include
without limitation phosphoric acid-kieselguhr,
copper-pyrophosphate-charcoal, and phosphoric acid-coated quartz
chips. Commercial processes include the CATPOLY.TM. Process (UOP
and Sud Chemie) employing phosphoric acid on a silica support.
Further catalysts are disclosed in the claims, description and
examples of EP-A-0 570 411, U.S. Pat. No. 6,025,533 and EP-A-1 694
617.
[0120] The OCTOL.TM. Process (UOP/Huels (now Evonik)) employing a
nickel containing catalyst on a silica/alumina support is also
useful. Amorphous silica alumina supports are useful and commonly
utilized. Solid acid catalysts may be optionally practiced with
promoters such as, for example, TaF5.
[0121] The catalysts utilized in the oligomerization processes may
be any suitable zeolite catalyst(s) capable of oligomerizing
olefins. Exemplary methods and materials are provided in WO
2012/033562, U.S. Pat. No. 4,973,790, and US-A-2012/0022224.
[0122] The at least one zeolite catalyst may include a medium pore
size molecular sieve having a Constraint Index of about 1 to about
12. Constraint Index and a method of its determination are
described in, for example, U.S. Pat. No. 4,016,218.
[0123] Preferably, the at least one zeolite catalyst is selected
from at least one of ZSM-5, ZSM-11, ZSM-12, ZSM-18, ZSM-22, ZSM-23,
ZSM-35, ZSM-38, ZSM-48, ZSM-50, ZSM-57, ITQ-39 and mixtures
thereof. The at least one zeolite catalyst comprises molecular
sieves having pores formed by 10-membered rings of tetrahedrally
coordinated atoms, such as molecular sieves having the TON or MFS
structure type.
[0124] Mixtures of two or more of catalysts may be used in the
processes of the present invention. For example, the mixture may
include ZSM-22 and ZSM-57 or ZSM-22 and ZSM-5 or ZSM-57 ZSM-5 and
ITQ-39. The at least one zeolite catalyst may also be combined with
other catalysts such as a solid phosphoric acid (sPa) catalyst or
other acid catalysts.
[0125] The zeolite used in the oligomerization catalyst may have an
average crystallite or particle size of up to 15 .mu.m, such as
within the range of from 0.01 to 6 .mu.m, alternatively, from 0.05
to 5 .mu.m, and alternatively, from 0.1 to 3 .mu.m. As used herein,
"average particle size" refers to the arithmetic average of the
diameter distribution of the crystals on a volume basis.
[0126] Preferably, the zeolite is used in its proton, or acidic
form. To obtain this form, an as-synthesized molecular sieve that
has been obtained in an alkaline or alkaline-metal form is
advantageously converted to its acid form, for example, by acid
treatment, e.g., by HCl, acetic acid, etc. or by ion exchange, for
example, ammonium ion exchange. Subsequently, it may undergo
calcination before use. The calcined materials may be post-treated,
such as by steaming.
[0127] The at least one zeolite catalyst may be produced by any
suitable method known for the given type of zeolite.
It may be desirable to incorporate the molecular sieves or zeolites
mentioned above with another material that is resistant to the
temperatures and other conditions employed in the olefin
oligomerization process. Thus the molecular sieves or zeolites may
be used in the form of an extrudate with binder, where the
molecular sieve or zeolite is dispersed within a conventional
binder as disclosed hereabove in connection with the
adsorbents.
[0128] In the context of oligomerization, suitable reaction
conditions may include temperatures from about 80.degree. C. to
about 350.degree. C. Close to and above the upper end of the range,
cracking rates increase and may predominate over the
oligomerization reaction providing an upper limit to practical
operation. More typically, the reaction temperature is from about
130.degree. C. to about 320.degree. C., preferably from about
135.degree. C. to about 310.degree. C., and even more preferably
from about 160.degree. C. to about 270.degree. C.
[0129] The pressure may be in the range of from about 400 psig to
about 4000 psig (2860 to 27688 kPa), and alternatively, from about
500 psig to about 1500 psig (3550 to 10446 kPa). The olefin weight
hourly space velocity based on catalyst, may be in the range of
from about 0.1 hr.sup.-1 to about 20 hr.sup.-1 or from about 0.5
hr.sup.-1 to about 5 hr.sup.-1.
[0130] In one embodiment, process is conducted at a temperature of
80-350.degree. C.; an olefin weight hourly space velocity of 0.1-20
hr.sup.-1, and a pressure of 2860-27688 kPa.
[0131] In another embodiment, the process is conducted at a
temperature of 130-320.degree. C.; an olefin weight hourly space
velocity of 0.5-5 hr.sup.-1; and a pressure of 3550-10446 kPa.
[0132] Optionally, the olefin feed may also be hydrated (i.e.,
contacted with water) prior to oligomerization. In an embodiment,
sufficient water is used to saturate the feed. In particular, the
feed may comprise from about 0.01 to about 0.25, alternatively,
from about 0.02 to about 0.20, and alternatively, from about 0.03
to about 0.10, mol % water based on the total hydrocarbon content
of the feed. If desired and by way of example, the water content of
the feed may be increased by passage through a thermostatted water
saturator. The olefin feed used in the oligomerization step can
therefore be wet or dry.
Hydrocarbon Products
[0133] The invention is particularly but not exclusively concerned
with processes suitable for the production of C5 to C20 olefins
boiling in the range of 30.degree. to 310.degree. C., preferably
30.degree. to 300.degree. C., more preferably 30.degree. to
250.degree. C., from propylene and/or butene and/or pentene
containing feedstocks or their mixtures, though ethylene may be
present as well. The oligomer product may be fractionated in a
series of discrete products. In particular the invention is
concerned with the production of the olefins shown in the following
table.
TABLE-US-00001 Distillation Range (.degree. C.) ASTM D1078 Oligomer
Products Initial Boiling Point Dry Point Pentenes 30 Hexenes 35 72
Heptenes 88 97 Octenes 114 126 Nonenes 135 143 Decenes 155 160
Undecenes 167 178 Propylene Tetramers 175 225 or Dodecenes
Tridecenes 204 213
[0134] The oligomer products are useful in many applications and
are the starting material for further processes. For example, the
oligomer product may be polymerized to produce polyolefins that
have application in the plastic industry and synthetic basestocks
for lubricants. The oligomer product may be used in alkylation
reactions for the product of surfactants. The oligomer products may
be reacted with sulphur containing compounds to produce mercaptans.
The oligomer product may undergo hydroformylation and subsequently
hydrogenation to produce alcohols. The alcohols may be used in
industry such as, for example, solvents, or be incorporated into
the production of detergents/surfactants. The alcohols may further
be used in many other areas of industry such as, for example,
undergoing esterification to produce esters that have application
as plasticizers. Oligomer products may be hydrogenated to produce a
predominately paraffin product such as ISOPAR.TM..
[0135] Products could be streams suitable for blending into fuels
dispositions including Mogas, distillate, diesel, jet fuel etc.
from processes like EMOGAS (ExxonMobil Olefins to Gasoline), MODG
(Mobil Olefins to Diesel and Gasoline).
EXAMPLES
[0136] The examples illustrate that when using a process according
to the invention, it is possible to significantly or even fully
restore the initial capacity for the adsorption of
nitrogen-containing compounds such as PCN after each
adsorption/regeneration cycle. This result represents a
considerable improvement in dealing with the potentially harmful
effects of nitrogen-containing impurities, dienes and cyclic
olefins present in hydrocarbon feed materials of interest.
[0137] In the following examples, the process of the present
invention is illustrated by means of a number of tests using NaY
extrudates as the adsorbent. In examples 1 and 2, the NaY extrudate
were crushed and sieved to 0.4 to 0.6 mm size. The adsorbent used
in examples 3 to 8 is the commercially Zeolite Na-Y available from
Zeolyst as ZEOLYST.TM. CBV 100 CY (1.6) characterized by white rods
of 1/16 inch diameter and by a ratio of zeolite (faujasite) to
binder of 80:20. Before passing the feedstock over the adsorbent,
the adsorbent was pretreated at 230.degree. C. for 24 hours in dry
nitrogen.
[0138] Then, an adsorption cycle using the pretreated adsorbent was
carried out. The adsorption took place in a tubular reactor at
40.degree. C. and a weight-hourly-based-velocity (WHSV) of 3.2
h.sup.-1.
[0139] Regeneration is carried out in the same unit at conditions
disclosed in the examples.
Example 1
[0140] In this example, a feed stream having the following
composition was passed over the NaY adsorbent.
TABLE-US-00002 Component wt % 1-pentene 98.6 1,3-pentadiene 1
Isoprene 0.4 PCN 80 ppm H.sub.2O 100 ppm
[0141] Regeneration was carried at 230.degree. C. using decene as a
regeneration stream at a WHSV of 3.2 h.sup.-1.
[0142] The results are shown in FIG. 1 in terms of the increase in
the level of PCN in the feed passing over the adsorbent, based on
the amount of feed per amount of adsorbent (wt feed/wt ads). After
passing a certain amount of feed over the adsorbent, as the
adsorbent's capacity is progressively being lost due to adsorption
of PCN and other species having an affinity to the adsorbent
material such as dienes, the concentration of PCN in the feed
stream raises toward the level of 80 ppm. In the first adsorption
cycle, the breakthrough of PCN sets in at about 750 wt feed/wt ads.
After regeneration in accordance with the procedure as defined
above, but for a longer time (decene at 230.degree. C. for 24 h and
at WHSV=3.2 h.sup.-1), when the feed is passed again over the
adsorbent, the onset of the increase in the content of PCN is at
about 450 wt feed/wt ads (2.sup.nd cycle). After a further cycle of
regeneration in accordance with the above conditions, the onset of
breakthrough of PCN is even earlier, i.e., at about 250 wt feed/wt
ads (3.sup.rd cycle). The earlier breakthrough of PCN illustrates
that adsorption capacity is progressively lost when dienes are
present in the olefin (1-pentene) feed and regeneration is carried
out by using decene as the regeneration stream.
Example 2
[0143] In this example, a feed stream having the following
composition was passed over the NaY adsorbent.
TABLE-US-00003 Component wt % 1-pentene 99.4 cyclopentene 0.6 PCN
80 ppm H.sub.2O 100 ppm
[0144] Regeneration was carried out at 230.degree. C. using decene
as a regeneration stream at a WHSV of 3.2 h.sup.-1.
[0145] FIG. 2 illustrates the results in terms of the increase in
the level of PCN in the feed passing over the adsorbent, based on
the amount of feed per amount of adsorbent (wt feed/wt ads). In the
first cycle, the increase sets in at about 1200 wt feed/wt ads.
After regeneration in accordance with the procedure as defined
above, when the feed is passed again over the adsorbent, the onset
of the increase in the content of PCN is at about 500 wt feed/wt
ads (2.sup.nd cycle). After a further cycle of regeneration in
accordance with the above conditions, the onset of the increase in
the level of PCN is even earlier, i.e., at about 400 wt feed/wt
ads. The earlier onset of the increase in the level in PCN
illustrates that adsorption capacity is progressively lost when
cyclopentene is present in the olefin (1-pentene) feed and
regeneration is carried out by using decene as the regeneration
stream.
Example 3
[0146] This example presents a comparison between a regeneration
procedure using decene at the conditions as detailed in Examples 1
and 2 and regeneration with a water-saturated nitrogen stream under
the same temperature conditions. The feed stream used in this
example had the following composition:
TABLE-US-00004 Component wt % 1-pentene 98.6 1,3-pentadiene 1
Isoprene 0.4 PCN 80 ppm H.sub.2O 100 ppm
[0147] The water-saturated nitrogen stream was passed over the
adsorbent at a flow of 25 ml/min, or about 12 h.sup.-1 WHSV, a
partial water pressure of 19.9 kPa (=vapor pressure of H.sub.2O at
60.degree. C.) and at a temperature of 230.degree. C.
[0148] The results are shown in FIG. 3 in terms of the increase in
the level of PCN in the feed passing over the adsorbent, based on
the amount of feed per amount of adsorbent (wt feed/wt ads). While
the increase in the level of PCN when using fresh adsorbent sets in
at about 800 wt feed/wt ads, after regeneration with decene the
increase sets in at about 400 wt feed/wt ads. However, when
regenerating in a water-saturated nitrogen stream, the onset of the
increase in PCN occurs at about 600 wt feed/wt ads only. Thus, as
compared to the use of a decene stream, under the same conditions,
when using a water-saturated nitrogen stream, the loss in
adsorption capacity after the 1.sup.st cycle is reduced by about
50%.
Example 4
[0149] This example illustrates a further embodiment of the use of
a water-containing nitrogen regeneration stream in which a first
regeneration step is carried out at 40.degree. C. and a second
regeneration step is carried out at 230.degree. C. The feed stream
used in this example had the following composition:
TABLE-US-00005 Component wt % 1-pentene 98 1,3-pentadiene 1
Isoprene 0.4 Cyclopentene 0.6 PCN 80 ppm H.sub.2O 100 ppm
[0150] Regeneration using a water-containing nitrogen stream at a
flow F=25 ml/min or 12 h.sup.-1 WHSV was carried out in the same
unit using a two-step procedure with a first regeneration step at a
temperature of 40.degree. C. for 48h and a second regeneration step
at 230.degree. C. for 24h followed by cooling down to 40.degree. C.
in a stream of dry N.sub.2. However, in the 3.sup.rd cycle, the
drying step was shortened. The vapor pressure (VP) of H.sub.2O in
the various regeneration cycles was:
[0151] 1) VP (1.sup.st cycle)=2.6 kPa (vapor pressure of H.sub.2O
at 22.degree. C.)
[0152] 2) VP (2.sup.nd cycle)=19.9 kPa (vapor pressure of H.sub.2O
at 60.degree. C.)
[0153] 3) VP (3.sup.rd cycle)=19.9 kPa (vapor pressure of H.sub.2O
at 60.degree. C.)
[0154] 4) VP (4.sup.th cycle)=19.9 kPa (vapor pressure of H.sub.2O
at 60.degree. C.)
[0155] 5) VP (5.sup.th cycle)=2.6 kPa (vapor pressure of H.sub.2O
at 22.degree. C.)
[0156] The results are shown in FIG. 4 in terms of the increase in
the level of PCN in the feed passing over the adsorbent, based on
the amount of feed per amount of adsorbent (wt feed/wt ads). The
combination of a water-containing nitrogen stream and a two-step
temperature treatment allows for full regeneration of the adsorbent
after each cycle. The results obtained in cycle 3 are ascribed to
an insufficient degree of drying after the high temperature
regeneration step leading to presence of adsorbed water after
cooling to 40.degree. C., which decreased NaY adsorption capacity
for PCN. However, the initial capacity was fully recoverable in the
following cycles.
[0157] Without wishing to be bound by a specific theory, it is
believed that the use of the initial low temperature step allows
dienes to desorb before they may oligomerize/polymerize as
consequence of the high temperature step. The presence of water in
the regeneration stream further supports desorbing the dienes. As
water is the most polar molecule present in the system, it will
compete for adsorption sites occupied by other molecules thereby
displacing them away.
Example 5
[0158] This example illustrates an embodiment using a dry nitrogen
regeneration stream in a first regeneration step at 40.degree. C.
and a second regeneration step at 230.degree. C. The feed stream
used in this example had the following composition:
TABLE-US-00006 Component wt % 1-pentene 98.6 Isoprene 1.4 PCN 80
ppm H.sub.2O 100 ppm
[0159] Regeneration was conducted by using a dry nitrogen stream at
a WHSV of 3.2 h.sup.-1 at 40.degree. C. for 24h followed by
regeneration at 230.degree. C. for 24h. The nitrogen flow F was 35
ml/min. After a total regeneration time of 48 h, the adsorbent was
cooled down to 40.degree. C. while still passing dry nitrogen over
the adsorbent.
[0160] The results are shown in FIG. 5 in terms of the increase in
the level of PCN in the feed passing over the adsorbent, based on
the amount of feed per amount of adsorbent (wt feed/wt ads). It can
be seen that the original capacity of the adsorbent was restored
when using the two step procedure as described in this example.
Example 6
[0161] This example illustrates the process of the present
invention when using a feed subjected to distillation and
hydrogenation prior to contacting with a NaY adsorbent as specified
above. The feed characteristics are summarized in Table the
below.
TABLE-US-00007 Feed composition after distillation and
hydrogenation. Hydrogenation Feed Hydrogenation Composition
(Distilled LLCN) Product <C4 sats 0.0000 0.0054 <C4 olefins
0.0001 0.0071 <C4 dienes 0.0000 0.0000 Isobutane 0.0027 0.0062
n-Butane 0.0180 0.0272 Isobutene 0.0015 0.0020 n-Butenes 0.0448
0.0635 C4 dienes 0.0000 0.0000 C4 cyclis (ol + sat) 0.0000 0.0000
Isopentane + 2,2 di-Me-Propane 38.7109 36.1152 n-pentane 6.2382
7.9259 Isopentenes 27.0843 28.5341 n-pentene 26.1323 26.5060 C5
dienes 1.2445 0.2889 C5 cyclis (ol + sat) 0.4235 0.4746 Hexenes
0.0953 0.0417 C6 sats 0.0018 0.0056 C6 cyclis (ol + sat) 0.0000
0.0000 C6 dienes 0.0000 0.0000 Heptenes 0.0022 0.0002 C7 sats
0.0000 0.0000 C7 cyclis (ol + sat) 0.0000 0.0000 C7 dienes 0.0000
0.0000 > C8 0.0000 0.0000 Sum Unknowns 0.0000 0.0000 Total Oxy's
(area %) 0.0000 0.0000 SUM hydrocarbons 100.0000 100.0035
[0162] Specifically, the feed was distilled light liquid catalytic
naphta (LLCN) obtained by the process described in the co-pending
European application EP15150687.0. The selective hydrogenation was
performed using a Pd on alumina catalyst LD-265 available from
Axens under the following conditions:
TABLE-US-00008 Pressure Bar 17-18 C5 rate g/h 2000 H2/dienes ratio
Mol/mol 0.5-1.6 Temperature C. 65 Operating Mode Down flow
[0163] After carrying out an initial adsorption cycle using the
feed hydrogenation product as specified above, the adsorbent was
subjected to regeneration. The 1.sup.st to 4.sup.th regeneration
cycles were performed by using water-saturated nitrogen gas
(partial pressure H.sub.2O=19.9 kPa (=vapor pressure of H.sub.2O at
60.degree. C.)) at a flow of 25 ml/min or 12 h.sup.-1 WHSV. In each
cycle, the water-containing nitrogen gas stream was passed over the
adsorbent at 40.degree. C. for 24 h followed by an increase to a
temperature to 300.degree. C. for another period of 24 h followed
by dry nitrogen at 300.degree. C. for 22 h. After a total period of
60 h, the adsorbent was cooled down to ambient temperature while
still passing dry nitrogen over the adsorbent. The results are
shown in FIG. 6 in terms of the increase in the level of PCN in the
feed passing over the adsorbent, based on the amount of feed per
amount of adsorbent (wt feed/wt ads). It can be seen that the
initial capacity of the adsorbent can be restored to acceptable
levels. Specifically, the onset of the increase in the level of PCN
occurs only after significant amounts of feed have been passed over
the adsorbent.
Example 7
[0164] This example illustrates the process of the present
invention when using a feed subjected to distillation prior to
contacting with a NaY adsorbent as specified above. The feed
characteristics were as stated hereinabove. The adsorbent was made
and pretreated as described in Example 6. The regeneration
procedure was as described in detail in Example 6. The results are
shown in FIG. 7 in terms of the increase in the level of PCN in the
feed passing over the adsorbent, based on the amount of feed per
amount of adsorbent (wt feed/wt ads). In comparison to the results
reported in Example 6, it can be seen that the initial capacity of
the adsorbent may not be restored to acceptable levels if too high
a level of dienes is present in the feed. Then, as illustrated by
Example 6, suitable hydrogenation ensures that the desired levels
of regeneration are achieved.
Example 8
[0165] This example illustrates treating (purifying) the spent
nitrogen stream resulting from the regeneration process according
to the present invention with low vapor pressure hydrocarbons to
remove nitrogen-containing organic impurities such as PCN present
in the stream.
[0166] FIG. 8 illustrates a regeneration process in accordance with
the invention using water containing nitrogen. Water is added to
nitrogen by injecting low pressure steam and the combined stream is
used to regenerate the adsorbent. The spent nitrogen gas is washed
with a saturated hydrocarbon with an initial boiling point of
162.degree. C. and final boiling point of 177.degree. C.
commercialized under the denomination Isopar.TM. G by ExxonMobil to
recover part of the water, the nitrogen containing compound and
other compounds desorbed from the adsorbent. Water is removed from
the saturated hydrocarbon in a settling drum and routed to an
appropriate water treatment system (e.g. sour water stripper).
[0167] The washed nitrogen containing the saturated hydrocarbon is
disposed of safely and within environmental permitting limits. To
recover the saturated hydrocarbons from this nitrogen stream, the
nitrogen stream is cooled and then disengaged from the saturated
hydrocarbons in a knock-out drum before venting to atmosphere.
Examples 9 and 10
[0168] These examples illustrates the process of the invention when
using a regeneration stream consisting essentially of saturated
hydrocarbons
[0169] The adsorbent was identical to the one used in examples 1
and 2 above and the feed stream has the following composition.
TABLE-US-00009 Composition wt % <C4 sats 0.02 <C4 olefins
0.04 <C4 dienes 0.00 Isobutane 0.00 n-Butane 0.02 Isobutene 0.00
n-Butenes 0.13 C4 dienes 0.00 C4 cyclis (ol + sat) 0.00 Isopentane
+ 2,2 di-Me-Propane 36.22 n-pentane 7.52 Isopentenes 30.48
n-pentene 24.88 C5 dienes 0.016 C5 cyclis (ol + sat) 0.62 Hexenes
0.04 C6 sats 0.01
[0170] The regeneration stream is a saturated hydrocarbon with an
initial boiling point of 162.degree. C. and final boiling point of
177.degree. C. commercialized under the denomination Isopar.TM. G
by ExxonMobil.
[0171] Regeneration in example 9 was carried out with a first
regeneration step at 40.degree. C. for 5 hours, heating to
230.degree. C. at constant rate for 7 hours followed by a second
regeneration step at 230.degree. C. for 16 hours before cooling
down.
[0172] Regeneration in example 10 was carried out with a first
regeneration step at 40.degree. C. for 5 hours, heating to
100.degree. C. at constant rate during 3 hours, a second step at
100.degree. C. for 6 hours and heating to 230.degree. C. at
constant speed for 3 hours and a third step at 230.degree. C. for 3
hours before cooling down.
[0173] The results are shown in FIG. 9 in terms of adsorption
capacity of the adsorbent at 40.degree. C. over consecutive runs,
each runs being separated by a regeneration treatment of the
adsorbent. The results in example 10 show that the adsorption
capacity is maintained over at least three successive regeneration
runs when the regeneration includes an extra step at 100.degree.
C.
[0174] Without wishing to be bound by a specific theory it is
believed that such step improves the desorption of diolefins and/or
cyclic olefins while avoiding coking of the adsorbed diolefins
and/or cyclic olefins on the adsorbent.
Example 11
[0175] This example illustrates the conversion of a hydrocarbon
feed into a hydrocarbon product using a feed having a reduced level
of nitrogen containing compounds obtained by using the adsorbent
regenerated as disclosed in example 10 above. The hydrocarbon feeds
with the composition as indicated in the table below are subjected
to oligomerisation over a ZSM-57 catalyst.
TABLE-US-00010 Composition of the feed Compound wt % Propane 0.02
Propene 0.03 iso-butane 4.46 n-butane 8.85 1-butene 42.41
iso-butene 2.33 1,3-butadiene 0.17 t-2-butene 0 c-2-butene 0.02
iso-pentane 16.43 3-Me-butene-1 0.27 n-pentane 3.28 pentene-1 1.46
1,4-pentadiene 0.05 2-Me-butene-1 3.83 pentene-2-t 6.52 pentene-2-c
2.57 Isoprene 0.06 2-Me-butene-2 7.17 Total C5 olefins 21.82
[0176] Prior to contacting the catalyst, the feed is saturated with
water by passing upward a hydrator at 30.degree. C. The
oligomerisation reactor is equipped with an axial thermowel
containing a 3 point thermocouple. The reactor temperature was
varied between 170.degree. C. and 260.degree. C. to maintain
constant conversion while maintaining the pressure at 70 barg.
Reactor space velocity (WHSV) was varied in the range of 3.0 to 5.0
h.sup.-'. In example 11 and 12 butene conversion was controlled in
the range of from 70 to 90%. In example 13 the propylene conversion
was controlled at 90%.
[0177] The oligomerisation product is collected and analysed by gas
chromatography equipped with a Pt on alumina catalyst to
hydrogenate the olefins.
[0178] The C8 olefinic product has a branchiness of 2.1. The
branchiness of the C9 olefinic product is of 2.2.
[0179] In summary, the process of the present invention allows for
largely or fully restoring the initial adsorbent capacity. This is
associated with the advantage of reducing the downtime of a unit
using an adsorbent because the adsorbent cycle time is constant and
no progressive capacity loss is observed. This also allows for more
flexible plant operation, i.e., reloading adsorbent units with
fresh or regenerated adsorbent. The process of the present
invention has broad applicability. For example, it can be used in
any process in which in the feed dienes and cyclodienes are present
and/or in which there is a need for removing nitrogen-containing
impurities such as nitriles such as PCN or ACN. Also, the process
for treatment of the spent inert gas can be used in connection with
any process in which nitrogen-containing impurities are removed via
adsorption to fixed-bed adsorbents.
* * * * *